Welcome back, the Waltons. Hello again, Royle family. Take a bow, the Buckets. The "multi-generational household," where multiple generations of the same family share the same home, is booming again, thanks to austerity, unemployment, rising living costs, and housing shortages.

In the US, this trend, which started in the 1980's, has accelerated rapidly over the past three years. Prevalence of extended family households is heading back towards 1950's levels, fuelling what researchers have called "the largest increase in the number of Americans living in multi-generational households in modern history."

"The economic climate and other demographic factors have turned America back into a nation in which families increasingly live together and lean on each other; the post-war era in which households kept getting smaller and adult children and aging parents frequently lived alone now seems more of an aberration than a trend."

Note the "back to the future" aspect of this quote. The most up-to-date US data, compiled by the Pew Research center, shows that in 1940 (during the "Great Depression") a quarter of all US households had multi-generation family arrangements. Post war affluence meant that by 1980 this had slipped to 12%. By 2009 it was up to 16.7%. Between 2007 and 2009 (the modern "Great Depression") the total shot up by 5m to 51.4m.

Polls suggest the rapid recent increase is down to financial hardship caused by worklessness, shrinking wages, and home repossession triggered by the housing market crash. According to Generations United, of the families they surveyed:

• 40% reported that job loss, change in job status, or underemployment was a reason their family became a multigenerational household.
• 20% reported that health care costs prompted them to form a multigenerational household.
• 14% reported that foreclosure or other housing loss prompted them to form a multigenerational household.

The Pew Research Center suggests this is a self-help response to adversity, triggered by the need to grasp a "financial lifeline". As the introduction to its report published last month neatly argues:

"Without public debate or fanfare, large numbers of Americans enacted their own anti-poverty program in the depths of the Great Recession: They moved in with relatives."

My off the cuff search for equivalent data for the UK - I'm afraid I only found this, and this - suggests that the multigenerational household phenomenon is not quite so pronounced here, at least for now. These surveys suggest that the increasing numbers of people (a 27% rise between 2001 and 2010) who go down this route say they do it as lifestyle choice, for "happy family" reasons. For the moment, it seems the imperative of financial necessity - for younger generations priced out of the property market, say, and older family members seeking care and companionship - is less marked.

Multi-generational households have always been a self-help anti-poverty programme for the poor in the UK. They are most prevalent in some of Britain's most deprived areas, such as Brent in northwest London, Bradford and Merthyr Tydfil (some of these areas have high concentrations of Asian and Afro-caribbean families, where multi-generational living is more culturally ingrained).

US research suggests that pooling resources in this way can produce financial upsides for some poorer families. Even where income is lower, the loss can be offset by the benefits of on-hand childcare and day care for older family members. The Generations United report cites other, softer benefits, for example the so-called "Grandparent advantage," which explains, it says, evidence of higher developmental outcomes in the children of single parents who live in multi-generational households.

There are downsides too. It is easy to sentimentalise the rise in extended family households (as one commentator recently gushed, "old fashioned family values are back in vogue"). Generations United points out that for low income families, living together in this way is no panacea for poverty or joblessness. Many such households try and get by in homes that are chronically unsuitable for their needs, or simply too small. Overcrowding (not just of the multi-generational kind) is, as Shelter has pointed out, harmful to children's health, and is a cause of stress, depression, anxiety and ill-health.

Generations United has called on the US government to recognise the extended household phenomenon with a range of support programmes, such as protecting welfare benefits, introducing tax credits for carers, and exploring new housing design options.

In the UK, there is little evidence that policy has caught up with this trend. Indeed, for all that you might expect the "big-society"-ish aspects of multi-generational living for poorer families to appeal to ministers, the government's housing benefit reforms seem intent on crushing it.

Rather than encouraging potentially beneficial ways of living for poorer families, benefit caps and "non-dependant" deduction increases for housing benefit recipients are essentially, as the Chartered Institute of Housing (CIH) has pointed out, an "incentive for tenants to encourage their children to leave home and a disincentive to voluntary sharing."

• Increased demand for independent housing from people who previously shared
• Higher incidence of adult children falling out with their parents and being asked to leave the family home
• Tenants being less willing to care for their elderly parents in their own home

I asked Stephen Burke, director of the UK charity United for All Ages, about the growth in multigenerational households in the UK. He said that while there were clearly some positive aspects, not least in the potential to provide care for older members of the family, there was little in the way of policy to encourage this:

"The most important thing for the government is to recognise this is a growing trend for families. Once it recognises that, we need to work out how to make it happen, by reviewing polices on benefits, housing and social care."

• The Pew Research Centre definition of a multi-generational household includes households with: (a) Two generations: parents (or in-laws) and adult children ages 25 and older (or children-in-law); (b) Three generations: parents (or in-laws), adult children (or children-in-law), grandchildren; (c) "Skipped" generations: grandparents and grandchildren, without parents; (d) More than three generations.